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[Doctor Gollum]

One can only be certain about things they have seen or experienced first hand.

Dave may not have removed the sprockets, nor Mark, but that doesn't categorically mean that they haven't been.

Under the circumstances there's a reasonable argument for checking them.

[Raeturbo]

But the witness marks don’t fit with the cam pin idea🤷‍♂️

[YZ250]

One can only be certain about things they have seen or experienced first hand.

Dave may not have removed the sprockets, nor Mark, but that doesn't categorically mean that they haven't been.

Under the circumstances there's a reasonable argument for checking them.

I’d have to check a cam sprocket to satisfy my curiosity but having studied exploded view drawings of this engine, the cam pin (the sizes match) can only fall out, from what I can tell, if the bolt is removed. The slot that the pin sits in does indeed go all the way through the sprocket but there’s a ruddy great washer at the front stopping it from escaping. 

I’m guessing that the rubber/plastic fragments with the pins are part of GM#90571618 Gasket, timing belt cover NLS.    I’d forgotten that the timing belt cover had a gasket on it. The pins are the mystery though.

[JamesV6CDX]

From memory the camshaft locating “pins” are an integral feature of the camshaft (eg, part of the “mould” for want of a better word, and not an insertable pin.

And I think it’s inconceivable that all four would come out.

And actually - they can’t - because behind the bolts holding the pulleys onto the camshafts, there’s a huge washer which would prevent them coming out

I like the thinking but I think it’s barking up the wrong tree sadly

[YZ250]

From memory the camshaft locating “pins” are an integral feature of the camshaft (eg, part of the “mould” for want of a better word, and not an insertable pin.

And I think it’s inconceivable that all four would come out.

And actually - they can’t - because behind the bolts holding the pulleys onto the camshafts, there’s a huge washer which would prevent them coming out

I like the thinking but I think it’s barking up the wrong tree sadly

The exploded view of the engine show the pins as the part number that Enceladus posted earlier.    I fully agree James, as I posted above, if there was the remote chance of one falling out (all 4 at once nigh on impossible), the pin would be trapped between the solid camshaft on one side and the big washer on the other side. 
The plot thickens as the part number GM# 90501111 that Enceladus posted are 12. something long and 4.6 diameter.. Spooky.

[countrywoman]

I would undo one sprocket bolt just to make sure the pin was there.

[JamesV6CDX]

We do need to identify what they are, it’s pointless getting it running again if there are more dodgy pins likely to fall onto the Cambelt 

[Dave_G]

Morning. I can’t see any missing plastic or gasket on the belt cover. It doesn’t quite go all the way around. The last 6cm or so is absent on the 3-4 cam side, but then it has no slot to go into.

Am I safe taking off a sprocket? In terms of getting it back on accurately I mean.

[JamesV6CDX]

Morning. I can’t see any missing plastic or gasket on the belt cover. It doesn’t quite go all the way around. The last 6cm or so is absent on the 3-4 cam side, but then it has no slot to go into.

Am I safe taking off a sprocket? In terms of getting it back on accurately I mean.

Safe to remove with the crank at 4pm

You’ll need to remove the cam cover to hold the cam still (24mm from memory, spanner on cam)

1-3-5 bank is easier

I still don’t think it’s from The camshaft though

[Dave_G]

No it’s not James. Locked the sprocket and took it off. The pin is about 6.2mm diameter, awkward to get the micrometer in, mine are 4.2mm.

[STEMO]

I think there's too much thought going into where the pins came from, and I've a feeling we'll never know. One of them has obviously got between belt and roller/tensioner and caused the belt to slip.
I would get it timed up and, hopefully, running, then the mystery of the pins can be debated till kingdom come.

[Dave_G]

I tend to agree. That was my plan this morning but there was so much uncertainty about the cam sprocket pin that I thought a look wouldn’t hurt. And now it’s ruled out.

I’ll put back some of my over-enthusiastic dismantling and get the belt back on as accurately as possible.

Cheers.

[Dave_G]

Quick update. Belt back on as accurately as I can.

Turned over several times by hand and nothing nasty. All marks came back to the same positions.

Just tried a few seconds on the starter and that was OK too.

Need a new water pump now. Last one was a QH QCP3255.

[STEMO]

Quick update. Belt back on as accurately as I can.

Turned over several times by hand and nothing nasty. All marks came back to the same positions.

Just tried a few seconds on the starter and that was OK too.

Need a new water pump now. Last one was a QH QCP3255.

Ooooo.....it's getting exciting now 

[JamesV6CDX]

I think it’ll fire up and run. Possibly on all 6